Adsorptive Denitrogenation of Diesel Fractions by Mesoporous SBA15 Supported Transition Metal Phosphide.

摘要

Stringent environmental regulations on sulfur concentration in transportation fuels, has made ultra-deep desulfurization of diesel an important research topic. It is important to overcome the adverse effect of nitrogen-containing compounds (NCCs) to make an efficient hydrodesulfurization (HDS) process for ultra-low sulfur diesel production. One of the processes is to separate nitrogen compounds by adsorption at ambient temperature and pressure before HDS process. Light Cycle Oil (LCO) is one of blended components of diesel which contains a high concentration of sulfur and nitrogen. High capacity adsorbents Ni2P/SBA15 and WP/SBA15 for nitrogen adsorption from LCO have been developed. Urea matrix combustion (UMxC) method was found most suitable over three different methods. 7wt% Ni and 15.5wt% W are optimum metal loading. Nitrogen adsorption capacities of Ni2P/SBA15 and WP/SBA15 are 9.1mg/gm-adsorbent and 7.53mg/gm-adsorbent respectively which are higher than most of the reported adsorbents. Thermodynamic study reveals that the adsorption process is exothermic and thus physical adsorption has been occurred. A very fast adsorption rate has been observed from kinetic study. Second order kinetic model was observed for both adsorbents. Multilayer adsorption has been observed for these adsorbents from isotherm study as these two adsorbents follow Freundlich isotherm model. Physiochemical properties of the adsorbents have been evaluated by different characterizing methods. Mesoporous nature of both adsorbents has been confirmed by nitrogen adsorption desorption analysis as well as TEM analysis. Ni2P and WP have been observed well dispersed over SBA15 which is the key factor for their high adsorption capacity. NH3TPD result proves neutral nature of these two adsorbents.